Image dimension sizing on React sites

Sites with explicit width and height image dimension sizing have a good CLS most often: 93%, against 92% of all React sites. Sites with CSS aspect-ratio image dimensions have it least often, at 84%.

Explicit width and height is the most used: 88.3% of React sites.

Wix sets the image dimension sizing to explicit width and height on 98% of its sites, and 98% of Wix sites have a good CLS, against 92% of all sites.

PlatformImage dimension sizing on its sitesGood CLS

React sites with image dimension sizing 9,502 sitesExplicit width & height attributes 88%Unsized <img> (no width/height or aspect-ratio) 75%92%

Wix 5,802 sitesExplicit width & height attributes 98%Unsized <img> (no width/height or aspect-ratio) 71%98%

WordPress 2,334 sitesExplicit width & height attributes 94%Unsized <img> (no width/height or aspect-ratio) 81%85%

Explicit width & height attributes Unsized <img> (no width/height or aspect-ratio) CSS aspect-ratio only

Does the platform explain the image dimension sizing difference?

On Wix, 98% of sites with explicit width and height image dimension sizing have a good CLS, against 98% of Wix sites with unsized <img>. Within Wix, sites with explicit width and height and unsized <img> have a good CLS about equally often. On WordPress, 85% of sites with explicit width and height image dimension sizing have a good CLS, against 85% of WordPress sites with unsized <img>. Within WordPress, sites with explicit width and height and unsized <img> have a good CLS about equally often.

How browsers compute intrinsic aspect ratios from HTML width and height

User-agent stylesheets map HTML width and height attributes directly to an internal aspect-ratio property before the image file downloads. Across the web, 88.3% of sites size images with HTML width and height (93% good CLS), while 75.5% still include at least one unsized <img> (91% good CLS) and 5.0% use CSS aspect-ratio without HTML attributes (84% good CLS).